DTX for Descent 1 had a rudimentary patch feature that allowed a developer to include a PIG patch file with a mission pack for Descent 1 and a program called DTXPATCH that made a backup copy of the original Descent.pig and modified the first one with your new material, thus having 'custom' textures/music in Descent 1. Problem is, the DTXPatch program no longer works on XP or new OS. So not sure how to get this 'function' of DTX to work again. Furthermore, if its possible to 'patch' the Descent.pig file with new textures and music like so, isn't it possible to 'patch' Descent 1 robots with new ones? What is the feasibility of this?

On version 1.00 says something about that.
I also remembered that you can put your HXM files (as long as it only contains D1 robot entries) and rename it to something like .HX1 to work (can't remember well).

However, i don't know if this feature is still present on D1X-Rebirth.

EDIT: Found this on Devil 2.2lc2 site about D1X features support:

Devil will automatically add any PG1/DTX and HX1 files belonging to the level which is found in the level's directory.
For example, the files:

I can see that its possible. Because I'd like players to have the option to 'turn on' whenever they wish, new music, textures AND robots for Descent 1. Not just for the 50 level set I'm currently making, but it should be appliable to any other D1 mission set. So this, essentially can breath fresh air into all D1 missions, not just my upcoming one. I'm currently looking through hi-res Quake 2/3 textures for good matches to the existing D1 textures (Forgotten Fortress was a test subject in this) but I can't seem to find matches for all, which means I have to broaden my scope.

You can put new robots in D1 by modifying the stock .PIG, yes. I don't know whether DTX will let you go that far, but it's theoretically possible at least.

P.S. Using DTX patches in that D1X-introduced mode (.HX1 etc) is not supported by the original Parallax code - ergo if anyone is still using Descent 1.4a/1.5 - I doubt it, but it's worth knowing about - they won't be able to use it.

well I guess redistributed an entire PIG I guess is legal in this case since I'd be replacing every robot, every textures and every midi. What else is in there? Because basically, itd be a PIG file with nothing of the original content in it. Problem is the robots. I'm not sure there is a program out there that can replace D1 robots. DTX can help patch the PIG, but for editing the Descent 1 PIG directly and replacing all textures/music/robots, I do not know of a way to do this.

Also, Sirius, if this entire plan is feasible, I'll be using the entire cast of TEW robots, so a few texture alterations are probably in order to make it gel with the limited amount of robot textures Descent 1 has available. The bosses of TEW, unfortunately, two are going to make the cut, while the others are dropped. I'm thinking Boss 1: The Raptor and boss 6: Hangman are the neatest looking and are probably going to be our two boss candidates.

Well at least for custom Music I could say: Ship them as MP3/OGG so at least the new ports (XL, DXX) can play them directly. Not trying to be selfish, but we all face more and more problems getting HMP/MIDI running (observation based on user reports).

There may actually not be any tool to do it... the specs are there, but the only editors for most of the Descent package files except .HOG were made by DNet from my memory, and I don't recall any for .PIG files. DTX can manipulate textures within PIG files but I think it ignores everything else.

so let me get this straight, for new textures and music, etc. All I need is the .DX1 extension file with the same name as the mission to have it work with Rebirth, etc?
Furthermore, for new robots, should I create a HXM trying my very best to only stick with D1 related material (since RBOTEDIT includes D2 stuff and has eliminated some D1 material) and simply rename it to a HX1 file and it should run fine? I'm confused as to how it'll work.